The “always book on Tuesday” advice is half-myth, half-outdated. Airlines used to release fare changes overnight on Mondays, so by Tuesday morning the cheapest seats had filtered down to the public booking systems. That still happens, but with dynamic pricing it’s far less consistent.
What actually moves international fares is the booking window: the cheapest spot for long-haul leisure trips is usually 8-14 weeks out. Closer than 4 weeks, you’re paying a premium; further than 6 months, the airlines haven’t optimized yet.